An optical communication network employing wavelength division multiplexing (WDM) can simultaneously transmit a plurality of optical signals or optical channels at different wavelengths. Each optical channel may be modulated by the data (text, voice, video, etc.) being transmitted. Furthermore, for identification of each channel, an identification signal may also be modulated onto the channel. When a channel is to be subsequently identified, a portion of the mixed modulated optical signal may be retrieved and the identification signal demodulated.
The identification signal used to modulate the optical signal comprises a time-division multi-frequency signal, wherein transitions between successive frequencies may induce an unwanted signal disturbance that makes demodulation of the identification signal difficult. Attempts to solve the disturbance problem caused by such frequency switching remain unsatisfactory. For example, some proposals have been costly by calling for unnecessary additional hardware, or they have caused degradation of the optical signal itself. Therefore, a need exists for an improved method for optical identification demodulation in an optical communications network.